Biometrics is known as a technique for authentication by verifying an individual's identity. As biometric verification or recognition, fingerprint verification (see Japanese Patent Laid-Open No. 11-96363), iris recognition (see Japanese Patent Laid-Open No. 2003-14156), voice verification (see Japanese Patent Laid-Open No. 11-73196), face verification (see Japanese Patent Laid-Open No. 11-161791) and the like are being used.
A method of performing authentication by checking a plurality of features for verification to improve the authentication accuracy is known (see Japanese Patent Laid-Open Nos. 2001-331801 and 2003-186847).
For example, an individual identification apparatus disclosed in Japanese Patent Laid-Open No. 2000-102524 uses both face image recognition and iris recognition.
A method, apparatus and recording medium disclosed in Japanese Patent Laid-Open No. 11-253426 are used to perform authentication by means of a plurality of bionic features in accordance with rules of discrimination in a feature space obtained by combining the verification scores of the bionic features.
A personal authentication system is disclosed in Japanese Patent Laid-Open No. 2000-242786 as an arrangement for probabilistically performing authentication by using a combination of two or more of fingerprint verification, face verification, voice verification and handwriting verification.
An individual authentication apparatus disclosed in Japanese Patent Laid-Open No. 2001-109855 uses a method of performing primary authentication processing by different authentication methods and making a final determination by uniting the results of primary authentication processing.
In an individual authentication system disclosed in Japanese Patent Laid-Open No. 2000-148985, voice, part or the whole of a face image and body smell are used as living body information and determination for authentication is made by using the degree of similarity (or a feature amount) of the first living body information and the degree of similarity of the second living body information.
In a personal authentication system using bionic information as disclosed in Japanese Patent Laid-Open No. 2001-338295, evaluations for authentication are made, for example, by evaluating the matching rate by means of voice information when a plurality of registered persons to be verified whose face information matching rate is equal to or higher than a threshold value exist, or by performing threshold value processing including multiplying together the face information matching rate and the voice information matching rate.
The above-described techniques using a plurality of features for verification lack consideration of the quality of feature detection signals used for verification and therefore entail a substantial problem that, for example, in a case where feature measurement conditions are not good and the SN ratio is considerably low, the error occurrence rate is increased relative to that in the case of collation using only good-quality feature detection signals.
For example, a person looks variously depending on the angle at which he/she is viewed, the distance through which he/she is viewed, his/her physical condition, an illumination condition, etc. In many cases of personal recognition where there is a need to recognize any person even under an unfavorable image taking condition, the recognition accuracy cannot be increased even if recognitions are made by integrally combining living body information items including face information or by using a predetermined method so that objects to be recognized are narrowed down.
Conventionally, there is a need to set a situation in which a subject is positioned just in front of a camera or made to utter a voice according to a voice instruction for authentication. The subject is thereby made conscious of being subjected to authentication. For this reason, personal recognition (authentication) cannot be performed on a subject of authentication with high accuracy while keeping the subject in a natural state without placing any burden on the subject.